From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8433AC6FD18 for ; Tue, 18 Apr 2023 14:26:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231177AbjDRO0j convert rfc822-to-8bit (ORCPT ); Tue, 18 Apr 2023 10:26:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230429AbjDRO0f (ORCPT ); Tue, 18 Apr 2023 10:26:35 -0400 Received: from gloria.sntech.de (gloria.sntech.de [185.11.138.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 878B719BD; Tue, 18 Apr 2023 07:26:32 -0700 (PDT) Received: from ip4d1634d3.dynamic.kabel-deutschland.de ([77.22.52.211] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1pomHo-0003qq-MP; Tue, 18 Apr 2023 16:26:24 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Peter Geis , Javier Martinez Canillas Cc: linux-kernel@vger.kernel.org, Peter Robinson , Caleb Connolly , Jarrah Gosbell , Krzysztof Kozlowski , Martijn Braam , Ondrej Jirman , Rob Herring , Tom Fitzhenry , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org Subject: Re: [PATCH] arm64: dts: rockchip: Change serial baud rate for Pinephone Pro to 1.5 MB Date: Tue, 18 Apr 2023 16:26:23 +0200 Message-ID: <3797122.KgjxqYA5nG@diego> In-Reply-To: <87h6tdie46.fsf@minerva.mail-host-address-is-not-set> References: <20230403175937.2842085-1-javierm@redhat.com> <3999080.iIbC2pHGDl@diego> <87h6tdie46.fsf@minerva.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi, Am Dienstag, 18. April 2023, 14:11:53 CEST schrieb Javier Martinez Canillas: > Heiko Stübner writes: > > Hello Heiko, > > > Hi Peter, > > > > Am Dienstag, 4. April 2023, 14:52:02 CEST schrieb Peter Geis: > >> On Tue, Apr 4, 2023 at 3:55 AM Heiko Stübner wrote: > >> > > >> > Hi, > >> > > >> > Am Montag, 3. April 2023, 19:59:37 CEST schrieb Javier Martinez Canillas: > >> > > This baud rate is set for the device by mainline u-boot and is also what > >> > > is set in the Pinebook Pro Device Tree, which is a device similar to the > >> > > PinePhone Pro but with a different form factor. > >> > > > >> > > Otherwise, the baud rate of the firmware and Linux don't match by default > >> > > and a 'console=ttyS2,1500000n8' kernel command line parameter is required > >> > > to have proper output for both. > >> > > >> > The interesting question is always if this will break someone else's setup. > >> > I've never really understood the strange setting of 1.5MBps, but on the > >> > other hand it _is_ a reality on most boards. > > > >> The 1.5M baud is default because the clock structure on rockchip > >> devices does not allow a clean 115200 baud. By attempting to force > >> 115200, it will always be slightly off (either low or high depending > >> on how the driver decided to round). If this actually causes any > >> problems is the subject of much debate. > > > > thanks so much for this piece of clock-detail. As I wrote, I never really > > understood the why _before_ but also never cared that much to dive > > into it and find out. > > > > So your explanation closes one knowledge gap in my head. > > > > Thanks a lot :-) > > Did you make a decision about this? I guess the clock explanation is yet > another argument in favour of switching the PPP to a 1.5 Mbps baud rate ? Sorry, but no decision made here. Either way it's breaking for someone, which makes this quite hard. The rate accuracy is the one side, the two-boot issue is the other side. And mainline u-boot (and levinboot - whatever that is) provides a 3rd side. People starting with the phone probably won't replace the bootloader in a first step but instead might play with a system image or newer kernel. So if the uart will break for everyone using the default bootloader from the factory that is somewhat bad. I don't have a Pinephone Pro myself, so I really hoped for some Acks or similar to appear in the meantime. Do we have someone with an actual Pine64 affiliation in this loop? Heiko